Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
  • B21J3/00—Lubricating during forging or pressing
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
  • C21D8/0236—Cold rolling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
  • B21B1/38—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling sheets of limited length, e.g. folded sheets, superimposed sheets, pack rolling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
  • B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/26—Methods of annealing
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
  • C21D8/0273—Final recrystallisation annealing
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C27/00—Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
  • C22C27/02—Alloys based on vanadium, niobium, or tantalum
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/08—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of copper or alloys based thereon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/10—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of nickel or cobalt or alloys based thereon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/14—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of noble metals or alloys based thereon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
  • C22F1/18—High-melting or refractory metals or alloys based thereon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
  • C22F1/18—High-melting or refractory metals or alloys based thereon
  • C22F1/183—High-melting or refractory metals or alloys based thereon of titanium or alloys based thereon
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
  • C23C14/34—Sputtering
  • C23C14/3407—Cathode assembly for sputtering apparatus, e.g. Target
  • C23C14/3414—Metallurgical or chemical aspects of target preparation, e.g. casting, powder metallurgy

Definitions

• the invention relates to metal articles with fine uniform structures and textures and methods of making such articles.
• metal articles of type described are especially useful as sputtering targets.
• Sputtering targets of high purity metals and alloys are widely used in electronics and semiconductor industries for sputtering thin films. It is desirable to obtain large size targets.
• the billet is forged at a temperature below the minimum temperature of static recrystallization and then rolled and annealed at a time and temperature to provide the beginning stage of static recrystallization.
• the rolling reduction per pass is desirably in accordance with a relationship of the minimum reduction per pass, the roll diameter and the desire billet thickness after forging. Generally, the reduction per pass during rolling is about 10% to 20% per pass.
• the invention comprises a metal article, such as a sputtering target, having a near-to-minimum of statically crystallized grain size, a difference in grain size at any location of less than about ⁇ 3% and a dispersion in orientation content ratio of texture of less than about ⁇ 4%.
• the present invention can be applied to different metals and alloys that display good ductility and workability at temperatures below corresponding temperatures of static recrystallization.
• metals with which the invention can be applied are Al, Ti, Ta, Cu, Nb, Ni, Mo, Au, Ag, Re, Pt and other metals, as well as their alloys.
• One embodiment of the method comprises the steps of processing an ingot to a semi-finished billet, including, for example, melting, ingot casting, homogenizing/solutionizing heat treatment, hot working to break down the cast structure, and billet preparation followed by billet shaping and thermomechanical treatment to fabricate a product, for example a sputtering target, and refine the metallurgical structure and produce a desired texture.
• cold/warm working and annealing are used to develop extremely fine, uniform structures and strong, uniform textures that result in improvement in performance of sputtering targets.
• FIG. 1 is a billet-film lubricant assembly at the beginning of upsetting
• FIG. 2 shows a sectional view "C" of FIG. 1 during upsetting
• FIG. 3 shows the beginning of rolling for long cylindrical billets
• FIG. 4 shows the beginning of rolling for short cylindrical billets
• FIG. 5 is a graph relating grain size and temperature for recrystallized structures showing effect of recrystallization annealing on grain size of pure Ti alloy after frictionless forging/rolling
• FIG. 6A is the microstructure of pure Ti after frictionless forging/rolling and annealing at 375 °C, 2 hours (x200 magnification);
• FIG. 6B is the microstructure of pure Ti after frictionless forging/rolling and annealing at 675 °C, 2 hours (x200 magnification);
• FIG. 7 A shows the dispersion in grain size of pure Ti after frictionless forging/rolling and annealing at 375 °C, 2 hours;
• FIG. 7B shows the dispersion in grain size of pure Ti after frictionless forging/rolling and annealing at 675 °C, 2 hours.
• FIG. 8 shows the effect of annealing temperature on texture (x-ray intensity ratios) of pure titanium after frictionless forging/rolling processing.
• targets are thin discs fabricated from a single billet processed by rolling or upsetting-forging operations. In both cases, an original billet length
• the original billet ratio (Mo) advantageously should be less than 1 , otherwise the end effect during rolling of long cylindrical billets develops very strong non-uniformity in strain distribution.
• the roll diameter advantageously should be significantly larger than the billet thickness and the number of reductions per pass can influence the result. Because of the foregoing, rolled billets may have concave-like shapes with maximum strain at contact surfaces and minimum strains at the middle billet section that are not sufficient to optimize recrystallization and develop most useful structures.
• Japan Patent No 08-269701 describes a titanium target manufactured by intensive cold rolling of sheet from stock and low temperature annealing. However, this technology cannot be applied to plates and although fine grain size is described for some target parts, the Japanese patent data shows large deviation in grain diameters.
• the patent describes a combination of forging and rolling for titanium targets at temperatures below the temperature of phase transformation.
• the process uses a temperature below the phase transformation temperature but well above the temperature of static recrystallization for heavy worked materials. As a result, the process cannot optimize recrystallization and develop very fine and uniform structures/textures.
• the present invention includes:
• the original billet (1) has a cylindrical shape and a volume and length- to-diameter ratio Mo.
• Two shallow pockets (2) are fabricated at the billet ends before upsetting. Cold upsetting is preferable, but in some cases preheating of the billet and tool to a temperature below the temperature of static recrystallization may be used to reduce working pressure and load.
• Two thin sheets of solid lubricant (3) are placed between the billet end and forging plate (4) mounted in a press. It has been found that best results are obtained with lubricant polymers that exhibit visco-elastic behavior at working conditions, such as polyethylene, polytetrafluroethylene or polyurethane. As can be seen in FIGS.
• film thickness( ⁇ ) is varied from about O.5 mm to 2.5 mm while film size (A) should exceed Do.
• Pocket depth ( ⁇ o) is advantageously slightly less than film thickness ( ⁇ ) and pocket borders (5) have a width "S" from about 5 mm to 20 mm.
• visco-elastic polymer film is used to entirely separate the billet and tool.
• the polymer fills the pockets and flows into contact with the billet.
• Some excess of polymer flows out from the pockets (FIG. 2) and provides low positive friction in the flow direction along billet ends, thus eliminating "dead metal” zones and improving billet stability.
• the preliminary forged billet is rolled for further reduction of thickness.
• Cold or warm rolling may be used.
• Rolling may be performed in two or four mutually perpendicular directions to produce a product with a circle-like shape. It is important to provide the most uniform strain distribution during rolling by controlling roll diameter-to-billet thickness ratios ( ⁇ /H), billet thickness-to-diameter ratio (M) and reductions per pass.
• An important aspect is to prevent buckling along the free surface (2) of a cylindrical billet ⁇ ) at the beginning of rolling (FIG. 3). It has been found that buckling area (T) is approximately equal to a billet-roll contact length (L), and buckling is eliminated if contact length exceeds a billet thickness hi after the first pass (FIG. 4). In other words, if L>H, then
• the roll diameter should be at least about 10 times (9.7 in Table 1) as large as the cylindrical billet thickness.
• use of thin billets for rolling without upsetting reduces possible reductions (1).
• Conventional target rolling suffer from both disadvantages, that is, non-uniform and low reductions are equally unacceptable to optimize structure.
• high ratios of roll diameter- to-billet thickness ( ⁇ /H) are provided by preliminary billet upsetting to the necessary thickness (H).
• the upsetting operation provides a pre-rolling billet ratio (m) of less than about 0.3 that is useful to attain uniform rolling reductions along a billet.
• Partial rolling reductions from about 10% to 20% per pass are also useful for near uniform strain distribution in the final product. Rolling reductions lower than about 10% develop higher strains at billet surfaces while reduction more than about 18% develop higher strains at billet middle section. All these parameters define the best embodiments for performing upsetting and rolling for targets for optimum results.
• the last step in target processing is recrystallization annealing.
• strains from equation (3) are enough to optimize static recrystallization.
• the lowest temperature necessary to start static recrystallization and then the shortest time necessary to complete that at all billet volume should be determined.
• Corresponding structures have the minimum grain sizes and the lowest dispersions of grain diameters inside each local area.
• the minimum temperature of static recrystallization may be realized as the optimal temperature for the whole billet at the shortest time. This results in very fine and uniform structures and strong, uniform texture for the target produced.
• Another embodiment of the invention is preforming forging in a few steps with successive decrease a billet thickness and resumption of film lubricant at each step. That way forging may be prolonged to low billet thickness without distortion of frictionless conditions and strain uniformity under relative low pressure and load. If forging is continued to the final target thickness without rolling, corresponding forging textures are provided for targets. Similarly, in the special cases rolling may be performed without forging with near uniform strain distribution in accordance with the invention.
• High purity titanium was cast into an ingot of 300 mm diameter and hot worked by swaging at a temperature of 800 C to a rod diameter of 130 mm. Billets of 162 mm length were then cut from the 130 mm rod. Pockets of 120 mm diameter and 1 mm thickness were machined at billet ends. Billets were upset at a temperature of 350°C to a thickness of 54 mm. Teflon films of 150 x 150 mm2 and thickness of 1.2 mm were used as lubricants for frictionless upsetting. Thereafter cold rolling with a roll diameter of 915 mm was performed in eight passes with partial reductions of 12% per pass along four directions under an angle of 45°.
• Coupons across the thickness of the rolled billet were cut from central, mid-radius and external areas and annealed at different temperatures during 2 hours (h). Two planes of coupons, one year the surface and the second near the middle section, were investigated for structure and texture and photomicrographs thereof are shown in FIGS. 6 A and 6B.
• tantalum sputtering targets were made by the process described above.
• the composition of the resulting tantalum target is shown in Table 2, the target comprising 99.95% tantalum and balance as shown in the table.
• FIG. 5 shows effect of annealing temperature on average grain size of titanium.
• the lowest temperature of static recrystallization is about 375 °C.
• Corresponding very fine structure of average grain sizes of 6 micrometers demonstrates also low local dispersion of grain diameter and strong texture (1013) (FIG. 8) with orientation content ratio of 65% in the perpendicular direction to target surface.
• An increase of annealing temperature results in intensive grain growth and larger dispersion in grain size with only moderate strengthening of texture.
• the photomicrographs shown in FIGS. 6 A and 6B show structures of pure Ti after frictionless forging/rolling and annealing at 375 ° C for 2 hours and annealing at 675 °C for 2 hours, respectively.
• FIGS. 7A and 7B depict graphically the dispersion of grain size of pure Ti for the structures shown in FIGS. 6A and 6B, respectively.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Organic Chemistry (AREA)
• Metallurgy (AREA)
• Materials Engineering (AREA)
• Crystallography & Structural Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Forging (AREA)
• Physical Vapour Deposition (AREA)
• Physical Deposition Of Substances That Are Components Of Semiconductor Devices (AREA)

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• 1998
  • 1998-06-17 US US09/098,761 patent/US6569270B2/en not_active Expired - Fee Related
  • 1998-06-26 KR KR10-2000-7000210A patent/KR100528090B1/ko not_active IP Right Cessation
  • 1998-06-26 EP EP98931689A patent/EP1027463A4/de not_active Ceased
  • 1998-06-26 JP JP2000502233A patent/JP2003532791A/ja not_active Withdrawn
  • 1998-06-26 WO PCT/US1998/013447 patent/WO1999002743A1/en not_active Application Discontinuation
• 1999
  • 1999-09-29 US US09/408,005 patent/US6238494B1/en not_active Expired - Fee Related

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